50 FLOWERS AND THEIR WORK 



off pollen but give the flower no return by cross-pollinating it. 

 In some flowers access of ants, plant lice, or other small crawling 

 insects to the stamens is rendered difficult by hairs which are 

 developed upon the filaments or on the corolla. Sometimes a 

 ring of sticky material is found making a barrier around the 

 stalk underneath the flower. Many other adaptations of this 

 sort might be mentioned. 



Artificial Cross-Pollination and its Practical Benefits to Man. - 

 Artificial cross-pollination is practiced by plant breeders and can 

 easily be tried in the laboratory or at home. First the anthers 

 must be carefully removed from the bud of the flower so as to elim- 

 inate all possibility of self-pollination. The flower must then be 

 covered so as to prevent access of pollen from without ; when the 

 ovary is sufficiently developed, pollen from another flower, having 

 the characters desired, is placed on the stigma and the flower 

 again covered to prevent any other pollen reaching the flower. 



The seeds from this flower when planted may give rise to plants 

 with some characters like each of the plants from which the pollen 

 and egg cell came. Artificial fertilization has been made of great 

 practical value to man. 



REFERENCE BOOKS 



ELEMENTARY 

 Sharpe, A Laboratory Manual for the Solution of Problems in Biology. American Book 



Company. 



Andrews, Botany all the Year Round, pages 222-236. American Book Company. 

 Atkinson, First Studies of Plant Life, Chaps. XXV-XXVI. Ginn and Company, 

 Bailey, Lessons with Plants, Part III, pages 131-250. The Macmillan Company. 

 Coulter, Plant Studies, Chap. VII. D. Appleton and Company. 

 Dana, Plants and their Children, pages 187-255. American Book Company. 

 Lubbock, Flowers, Fruits, and Leaves, Part I. The Macmillan Company. 

 Newell, A Reader in Botany, Part II, pages 1-96. Ginn and Company. 



ADVANCED 



Bailey, Plant Breeding. The Macmillan Company. 



Campbell, Lectures on the Evolution of Plants. The Macmillan Company. 

 Coulter, Barnes, and Cowles, A Textbook of Botany, Part II. American Book Com- 

 pany. 



Darwin, Different Forms of Flowers on Plants of the Same Species. D. Appleton & Co. 

 Darwin, Fertilization in the Vegetable Kingdom, Chaps. I and II. D. Appleton & Co. 

 Darwin, Orchids Fertilized by Insects. D. Appleton and Company. 

 Gray, Structural Botany. American Book Company. 

 Lubbock, British Wild Flowers. The Macmillan Company. 

 Muller, The Fertilization of Flowers. The Macmillan Company. 



